German patent document 1,602,864 suggests for better guiding and breaking of the moving chip over a greater machining region to form the cutting edge between the cutting corners as a concave arc and to leave the inner flanks of the chip-breaking groove steep to the respective overlying surface (plateau) of the cutting insert.
German patent document 2,544,991 describes a cutting insert that has more than two terraced chip-breaking steps along the cutting edge with each step edge having a longitudinally wavy edge. With this embodiment it is possible in another way to avoid a long helical chip with the last cutting insert in that optimally many and differently directed chip-deforming pressures are effective over the entire chip width so that same is deformed crosswise and transversely. In this above-cited embodiment the stated goal of making short chips is only unsatisfactorily obtained. From European patent documents 0,168,556 and 0,222,317 cutting inserts are known having a chamfer along the cutting edge and parallel to the cutting edge and chamfer a chip-guiding groove and a raised central part substantially above the chamfer and with ball-segment projections provided on the ascending flank to the raised central part. German patent document 3,431,601 describes a cutting insert with a first cylindrical chip-guiding groove of uniform width and a second cylindrical chip-guiding groove which is of greater width but lesser depth than the first groove.
The cutting insert according to European patent document 0,414,241 has recesses not only on the free surface but also on the cutting surface and which merge with one another in the region of the cutting edge so that the cutting edge is set back in the region of the recesses relative to the remaining parts of the cutting edge. The respective trapezoidal shape is made with sharp edges so that one cannot count on a long service life. In addition as always friction is very great on the cutting surface during chip removal. Disadvantageously the cutting insert in the named publication is only usable in specialized applications.
In order to ensure good chip formation even with widely varying rates of advance, cut depths, or advance speeds it has been suggested further in European patent publication 0,278,083 to provide a cutting angle of more than 30.degree. in the region extending on the chamfer at a right angle to the cutting edge so that the cutting angle is smaller with increased spacing from the chamfer and there is provided in the cutting surface region of the cutter body between the cutting-corner regions cutting ridges projecting out of the cutting surface and extending in the cutting direction and between which further bumps with run-on ramps are provided. The corners have three adjacent burred bumps which flank and extend parallel to the ridges.
European patent document 0,143,758 has longitudinally extending ridges which are trapezoidal in section and which run parallel to the cutting edge. These ridges are interrupted by recesses.